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Additionally, the leaching interval will be closely monitored through the use of 6 <br />monitoring /observation wells during the leaching phase, three wells found in the interior (unless <br />converted to an injection well) of the heater well configuration and three wells exterior of the <br />configuration. These wells are shown in Figure 2. The leach front will be monitored by changes in <br />temperature and pressure, rock temperatures will Increase ahead of the actual leaching front and at <br />some leach distance the temperature sensors will detect an increase. In addition, once the leaching <br />front breaks through to a well, pressure sensors will detect the increase in pressure as the leach well <br />pressure will be higher than formation pressure. <br />SUBSIDENCE MONITORING <br />The subsidence monitoring plan will include subsurface monitoring to detect subsurface movement. <br />Shell has elected not to provide for surface monitoring due to the width (20 feet radius) and depth of <br />the project (> 2,100 feet). Furthermore, the subsidence monitoring that is required is intended to <br />provide indication of subsurface movement well before surface movement is to occur. <br />Subsurface Subsidence <br />Shell is proposing to implement two subsidence monitoring technologies, time domain reflectometry <br />(TDR) and radioactive markers. The TDR has an advantage over other subsidence monitoring <br />methods in that the monitoring is a continuous process, whereas the radioactive markers are logged <br />periodically. Other subsurface monitoring techniques may be employed, provided the operator <br />submits sufficient information to demonstrate that the alternative will provide equivalent subsidence <br />monitoring to that of the existing monitoring technique, and the alternative monitoring technique is <br />approved by the Director. If approved, the Permit will be changed to Include the new alternative by <br />issuance of a Minor Modification. <br />Time Domain Reflectometry (TDR) <br />TDR is an electrical pulse- testing technique, whereby a pulse is created in the coaxial cable and <br />returns a reflected signal when the cable experiences a crimp or elongation. The TDR will be <br />installed In 0802 from the dissolution surface (2;013') to within 70 feet of the injection Zone (2,074 <br />feet). 0802 is 9.24 feet from H01, the injection well. Materials will be used that can withstand the <br />maximum anticipated temperature of the project. <br />Radioactive Markers <br />Radioactive pip tags wiILbe locatedin -to -the casing -on -0802 approximately every 20 feet from 1,800 <br />feet to 2,124 feet and in 0804 approximately every 20 feet from 1,800 feet to 2,270 feet that are <br />permanently cemented In the well. The tags consist of a weak gamma ray source such as Cobalt -60 <br />or Zinc-65 which produces a radiation level of 0.014 mrem/hr at one foot from the source. Shell <br />estimates, owing to the relatively short half -life of the radioactive marker (5.2 years for Co -60 and <br />240 days for Zn -65), the small size of the pip tag, their location in the casing collars, and their great <br />depths (greater than 1,500 feet), and given that no water wells exist in the zone to be monitored, the <br />risk of contact with. environmental receptor is estimated to be small to none. <br />The OB04(SAW) well is outside of the leached region and 0B02 is within. Shell states that <br />movements as small as 0.02 inches can be measured accurately. If the formation subsides (or <br />heaves) the casing cement will subside with it, and the casing will stretch due to the pressures. A <br />baseline log will be required to establish the original depths,of the radioactive markers and <br />subsequent monitoring will occur on a quarterly basis. The log run will also provide a signature of the <br />formation and can possibly detect more subtle changes to the formation that do not lead to casing <br />stretches, by comparing location of casing collar locator relative to the formation. <br />Shell has performed a geomechanical assessment, modeling a 130 feet by 20 feet radius cylinder. <br />The geomechanics model assumes that the entire leach volume is void and that the lower crown will <br />Permit CO32210 -00000 16 <br />`Y`" � • '•'t` %':;-�i�: Statement of Basis <br />